This application relates to and incorporates herein by reference Japanese Patent Application No. 2001-40245 filed on Feb. 16, 2001 and Japanese Patent Application No. 2001-345027 filed on Nov. 9, 2001.
1. Field of the Invention
The present invention relates to an idle speed control valve (ISCV) for controlling an air amount supplied to combustion chambers in an internal combustion engine. More particularly, the present invention relates to an idle speed control valve in which an adjusting screw including a stator core is sealed with a sealing material.
2. Description of Related Art
In general, in an internal combustion engine for a vehicle, a bypass pipe separate from an actual air intake pipe is provided to bypass a throttle valve. An idle speed control valve is provided in the bypass pipe to control an amount of fluid such as air flowing in the bypass pipe.
In a general idle speed control valve shown in FIG. 5, an adjusting screw 120 is inserted in a hole 115 provided in a valve body 111 and passes through a center of windings 130. As shown in FIG. 6, the adjusting screw 120 has a threaded portion 122 on its outer peripheral surface to be threaded with an inner wall of the hole 115. Adhesive is applied to the threaded portion 122 beforehand, so that the adjusting screw 120 fixes on the inner wall of the hole 115 at a desired position.
More specifically, first, an adjusting screw 120 in which the adhesive is not applied is temporary fitted in the hole 115 to adjust a spring for biasing a movable core 141 so that a movement area becomes a predetermined crossing area. Next, adjusting screw 120 is removed from the hole 115 and replaced with adjusting screw 120 with adhesive applied onto the threaded portion 122. Then, the adjusting screw 120 is finally adjusted and fitted at a predetermined position. Next, a sealing material 150 such as silicon is applied around a head portion 121 of the adjusting screw 120 to improve air-tightness. The sealing material 150 passes between the head portion 121 and the inner wall of the hole 115 and enters the inside of the hole 115. In this case, since the threaded portion 122 is bonded with the adhesive, the sealing material 150 stops at the threaded portion 122. (Not shown)
Since a replacement of the adjusting screw 120 is required, mounting and assembly time increase and workability is worsened. Thus, if the adjusting screw 120 in which the adhesive is not applied to the threaded portion 122 is used without pre-adjustment and adjusted to the final position, the sealing material 150 applied around the head portion 121 enters deeper inside the control valve 110 beyond the threaded portion 122. For example, when this sealing material 150 is hardened around a movable core 141, operation of the movable core 141 is interrupted, and as a result, a valve 145 will not operate.
In order to prevent entering of the sealing material 150 around the movable core 141 in the idle speed control valve 110, a rigid barricade portion may be provided on the outer periphery of the adjusting screw 120. However, when the barricade portion is press-fitted on the adjusting screw 120 foreign material accumulates and is likely to enter the idle speed control valve 110. Further, the adjusting screw having the barricade portion requires more torque to be inserted into the hole 115 when compared to that of the adjusting screw 120 without the barricade portion. Therefore, the inner wall defining the hole 115, and the adjusting screw 120, are likely to be damaged.
Accordingly, in a case where the adhesive is not applied to the threaded portion, the adjusting screw is required to be inserted without damage and also, the sealing material must be restricted from entering the idle speed control valve beyond the threaded portion.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
According to one embodiment of the present invention, an adjusting screw has a ring-shaped flexible projection on the outer peripheral surface thereof between a threaded portion and a head portion. The flexible projection projects from the outer peripheral surface of the adjusting screw in a radial direction. A width or depth of the flexible projection in a radial direction is substantially equal to a distance between the outer peripheral surface of the adjusting screw and an inner wall of a hole provided in an idle speed control valve body. Therefore, a peak of the flexible projection contacts the inner wall of the hole when the adjusting screw is inserted into the hole.
Accordingly, a sealing material, which is applied around a head portion of the adjusting screw for sealing between the outer peripheral surface of the adjusting screw and the inner wall of the hole, is prevented from entering inside of the idle speed control valve beyond the flexible projection. The width of the flexible projection in the radial direction can be greater than the distance between the outer peripheral surface of the adjusting screw and the inner wall. In this case, the peak of the flexible projection is bent backward (opposite to the direction of insertion) when the adjusting screw is inserted into the hole. Therefore, the entering of the sealing material is effectively prevented at the flexible projection.
According to another embodiment of the present invention, the adjusting screw has a thin wall portion on which a ring-shaped projection is provided between the threaded portion and the head portion. A width of the projection in the radial direction is greater than a distance between the outer peripheral surface of the thin wall portion and the inner wall of the hole in the idle speed control valve body. Therefore, when the adjusting screw is inserted into the hole, a peak of the projection contacts the inner wall and the thin wall portion having the projection is deformed toward an axial line of the adjusting screw. Accordingly, the sealing material is prevented from entering the inside of the idle speed control valve beyond the projection. Further, a threading torque of the adjusting screw is reduced.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for the purpose of illustration only and are not intended to limit the scope of the invention.